Sucker rods are rods, typically made of steel or other materials, providing a mechanical connection between the surface components and downhole components of a rod pumping system for use in an oil field. Sucker rods are elongate members that are conventionally about 25 to 30 ft (about 7 to 9 m) long and include threaded pins at their ends. Sucker rods can be connected to other components by means of a threaded box or other threaded connection engaging a threaded pin, and the rods enable pumping system downhole components to be reciprocated within and easily retrieved from the borehole.
The uppermost rod in a string of sucker rods passing down a borehole is referred to as a polished rod. The polished rod enables an efficient hydraulic seal to be formed around the reciprocating rod string. According to the American Petroleum Institute (hereinafter “API”), a polished rod connection should include a tapered or angled threaded connection between a threaded pin portion of the polished rod and a threaded box. The current practice is that the tapered portion of a polished rod's threads are cut using conventional thread-forming techniques. Additional information about and specific dimensions of polished rod connections may be found in API Specification 11B, 25th ed., Jan. 1, 1995 (hereinafter “API 11B”), herein incorporated by reference in its entirety. Also, additional information regarding polished rods and oil well pumps in general may be found in, for example, U.S. Pat. No. 5,769,161, entitled “POLISHED ROD FOR OIL WELL PUMPING,” hereby incorporated herein by reference in its entirety.
As is known, tapered threads are used in various other applications. For example, tapered pipe threads are employed in plumbing systems, as specified by, for example, the National Pipe Thread (“NPT”) Tapered Thread standard. Other items that may incorporate tapered threads include, for example, certain hydraulic and/or pneumatic fittings.